Tipping Points and Feedback Loops

Although climate change is caused by human emissions of greenhouse gases, it is also affected by tipping points and feedback loops that are a part of the Earth’s climatic system.

Tipping Points

Imagine a glass of milk on a table. Tip the glass a little, and not much happens. Tip the glass a little further, and still not much happens — the milk just sloshes in the glass. But, tip the glass far enough, and the milk will suddenly pour out onto the table. This moment of suddenly changing from one state (milk in glass, dry table) to another state (milk on table) is called a tipping point. Tipping points are generally preceded by gradual and low-impact changes (the milk sloshing around, but staying in the glass), occur quickly (the milk spilled rapidly onto the table) and cannot be undone (there is no way to put the milk back into the glass).

Many climate change scientists believe tipping points will play a role with climate change, and may affect the timing and severity of climate change impacts. For example:

The complete disappearance of Arctic sea ice during the summer months could dramatically change ocean currents in the Atlantic and Pacific Oceans.

The melting of permafrost could lead to a massive release of methane gas, thus greatly accelerating climate change.

A longer dry season, precipitated by a temperature increase of just 5-7 degrees Fahrenheit, could cause a rapid die-off of the Amazon rainforest.

Feedback Loops

When the output of a system affects itself, this is known as a feedback loop. A well-known example that affects climate change is the ice-albedo feedback loop. Ice has a higher reflectivity — albedo — than land or water. This means that ice is better able to reflect heat back into the atmosphere than bare land or water. However, because temperatures are rising, Arctic sea ice is melting more rapidly in the summer months. This exposes more water, and allows the oceans to absorb and retain more heat. This, in turn, increases the likelihood that even more ice will melt during the following summer.

Additional feedback loops include:

Stronger and more frequent droughts in some areas may cause a die-off of local vegetation. Because plants help maintain a certain level of humidity, this die-off could lead to worsening drought conditions in the future.